Accurately determining and indicating the amount of fuel contained within a fuel tank can often be critical for a vehicle operator. The fuel amount may be used to determine when and where the vehicle should be refueled prior to the fuel tank being emptied.
A typical fuel tank utilizes a dedicated fuel level sensor, such as a floating sensor, to determine the amount of fuel remaining in the fuel tank. However, if the floating sensor becomes stuck, malfunctions, or becomes decoupled from the vehicle powertrain control module, the fuel level may become unknown. An in-dash fuel level indicator may provide an inaccurate or indeterminate fuel level to the vehicle operator. This may lead to the vehicle running out of fuel if the fuel level indicator suggests fuel is still remaining in the tank, or may lead to increased operator anxiety stemming from not knowing how much fuel is remaining in the tank.
Periodically, diagnostic tests may be performed on the fuel level indicator. However, current tests often include monitoring output of the fuel level indicator over a period of 100 miles of engine combustion. For hybrid vehicles, and other vehicles capable of operating without engine combustion for long periods of time, the test may take a long time to complete. Further, the test does not cover the entire range of the fuel level indicator. A fuel level indicator that is prone to stick or has a worn resistive track that effects output only at certain fuel levels may go undiagnosed.
The inventors herein have recognized the above problems and have developed systems and methods to at least partially address them. In one example, a method, comprising indicating an amount of a residual fuel in a fuel tank based on an initial rate of change of a fuel tank pressure during a refueling event. The initial rate of change of fuel tank pressure is proportionate to the amount of vapor dome space within the fuel tank, and thus proportionate to the amount of residual fuel left in the fuel tank. In this way, the fuel tank fill level may be accurately quantified, even during cases where the fill level indicator experiences degradation. The method is applicable to fuel tanks configured to store and receive liquid fuel. The method may further comprise indicating an amount of fuel in the fuel tank based on a sum of an amount of fuel added during the refueling event and the indicated amount of residual fuel, the indicating via a display element in a vehicle in which the fuel tank is positioned. The amount of fuel added during the refueling event may be based on a steady-state fuel tank pressure during a refueling event. In this way, by monitoring fuel tank pressure during a refueling event, an accurate measure of fuel tank fill level may be determined without relying on inferring residual fuel based on total fuel consumed, which assumes fuel injectors do not leak and the fuel system is not otherwise compromised.
In another example, a method for a fuel system, comprising: indicating degradation of a fuel level indicator for a fuel tank based on an output of the fuel level indicator during a steady-state duration of a refueling event. During the steady-state duration of the refueling event, fuel is dispensed into the fuel tank at a constant rate. If the fuel level indicator output does not increase linearly and continuously during this duration, degradation may be indicated. In this way, fuel level indicator degradation may be indicated across the entire range of the fuel level indicator, without relying on methods that require correlating fuel consumption with fuel level indicator output decreasing. For hybrid vehicles, and other propulsion systems that may run for extended periods of time in non-combusting modes, this method provides increased rationality over a compressed timeframe for diagnosing fuel level indicator degradation.
In yet another example, a fuel system for a vehicle, comprising: a fuel tank configured to store liquid fuel; a fuel tank pressure transducer coupled to the fuel tank; a fuel level indicator coupled within the fuel tank; a controller configured with instructions stored in non-transitory memory, that when executed, cause the controller to: monitor an output of the fuel tank pressure transducer during a refueling event; monitor an output of the fuel level indicator during the refueling event; indicate an amount of residual fuel in the fuel tank based on an initial rate of change of a fuel tank pressure during the refueling event; indicate an amount of fuel added to the fuel tank based on a steady-state fuel tank pressure and further based on a steady-state duration; and indicating degradation of a fuel level indicator based on the output of the fuel level indicator during the steady-state duration of a refueling event. In this way, fuel fill level and fuel level indicator degradation may be determined during a single refueling event based on fuel tank pressure during the refueling event.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.